I'm interested in writing a C++ client for postgres which needs the ability to receive notification any time a value in the database, which the client deems important, changes (this can theoretically be any value in any column of the database). The conditions for this notification may change frequently over the course of the programs execution. What mechanisms exist in postgres to do this (I've briefly looked at triggers and Listen/Notify, just want to make sure I'm not missing something)? Which method is the most efficient, considering the constant need to update the trigger condition (or is it best to delete the old trigger and create a new one each time)?